Extension is proposed of preliminary studies on the fine structure of lung heparin and heparan sulfates already initiated in a program on acid mucopolysaccharide catabolism. It is hoped that the results of such structural studies and those of workers using other approaches may cast light on the nature, structures and functions of lung heparinoid proteoglycans and on their modes of biosynthesis and catabolism. Emphasis will be placed on the chemical fragmentation of the polysaccharides to identifiable, well-characterized, chemical compounds such as monosaccharides and oligosaccharides. The guiding principle will be that of accounting for a maximal proportion of the native polymer as such defined fragments. Beef lung heparin will be used as a model in selection of appropriate reference compounds, whose synthesis or isolation is to be undertaken, and for perfecting the necessary methodology. Work on heparan sulfate will exploit the findings for heparin, with adjustment, as required.